1. Field of the Invention
The invention relates to a method for the repetitive transmission of a signal representing a binary value via a transformer section of a driver of a power semiconductor.
2. Description of the Related Art
The driving of a power semiconductor, e.g., of a power semiconductor switch in the form of an IGBT (insulated-gate bipolar transistor), necessitates a so-called driver circuit, or a driver for short. By way of example, the driver generates a signal from a logical switching signal of weak power that is fed to the driver at the input. The signal is applied to the power semiconductor at the output of the driver and has significantly increased power, which is necessary, for example, for actually switching an IGBT. Moreover, the driver performs electrical or potential isolation between its input and output, e.g., the switching signal or a drive logic operating at earth potential (ground) and the power semiconductor, which operates at high-voltage potential.
In general, within this driver, therefore, a binary signal, i.e., a signal representing a binary value, is transmitted via a transformer section of the driver. The transformer effects the potential isolation in the signal to be transmitted. A corresponding binary signal is, e.g., a switch-on or switch-off signal for the transformer. A signal in the form of a switching signal has, e.g., only the two signal values “on” and “off”. In order to obtain a high switching reliability, it is customary to transmit corresponding signals or signal values repetitively. It is known, for example, when a switch-on signal is applied, to feed to the transformer as a first binary value—e.g., proceeding from a center potentia—repetitively positive voltage pulses. These pulses are fed to the transformer until a switch-off of the power semiconductor is desired. Proceeding from the center potential, repetitively negative voltage pulses are thereupon fed to the transformer.
During the presence both of the switch-on signal and of the switch-off signal, the transformer or the magnetization thereof attains positive or negative saturation as a result of repetitive application of the respective identical positive or negative voltage pulses. In order to avoid saturation of the transformer, it is known to utilize the time between two identical successive repetitively applied pulses as a recovery time for the transformer so that the latter can at least partly be demagnetized again. Therefore, it is necessary to have a minimum time or minimum dead time between two identical repetitive pulses.